Cementos Molins

Fixing tiles on floors with underfloor heating

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An increasing number of homes are fitted with underfloor heating surfacing due to the advantages it offers, including the considerable energy saving with respect to conventional heating systems.

There are two types, water underfloor heating and electric underfloor heating.

Underfloor heating with water pipes, is the most common one. The water circulates at a max. temp. of 45ºC and the surfacing surface temperature is 18-22ºC. Since the definitive thickness of the surfacing is about 95 mm, this system is usually installed in new buildings.

A – Stoneware (10 mm)

B – Tile cement (5 mm)

C – NIVELANTE 80 Mortar on pipes (40 mm)

D – Pipes (20 mm)

E – Insulation (20 mm)



Electrical underfloor heating with heating sheet or cable. This system uses electrical energy to heat a stainless steel cable. The definitive thickness of the surfacing is about 6 cm, therefore it is usually used when rehabilitating properties.

When starting the system, the bottom part of the mortar filling (next to the water pipes, approx. temp. 45ºC) expands more than the top part (approx. surface temp. 22-25ºC).

This generates shearing stress in the ceramic tiles, which could cause them to work loose.

For correct fixing that guarantees adherence, it is necessary to use very flexible and easy to apply adhesive mortars PAM® FLEXVAT® PORCELÁNICO FLEXVAT® FLEXIBLE, with a fluid consistency VAT® FLUID, or quick service VAT® FLEX RAPID.

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The mortar support must be resistant, completely set and free of any dust.

Check the smoothness of the support with a 2 m long ruler; any differences must be less than 5 mm.

The tiles must be fixed when the mortar is completely dry and with a degree of humidity no higher than 2.5%.


Mix with a slow electric mixer (500 rpm), spread and apply to the support using a notched trowel.

Press the tiles to ensure that they all form a solid surface, so that there are no gaps between the tile and support.

Leave a minimum grouting joint width of 2 mm and regrout after 24 hours using the grouting range BORADA® by PROPAMSA.


  • Do not apply in wet weather, or at temperatures <5ºC or >30ºC.
  • There must be expansion joints in the door spaces,for surfaces >40 m2 or when the length is more than 2  times the width.
  • The mortar support must be free of any dust and dirt before fixing the tiles.
  • Tiles should not be placed until to 48 hours from the application of NIVELANTE 80.
  • It is advisable to switch off the heating 48 hours before fixing the ceramics, and to not switch it back on again until at least 7 days after grouting.
  • Wrapping the water pipes or heating cable should be arranged in a layer of about 40-50 mm of VAT® FLUID.
  • It is necessary to always be double glued for the placement of parts, except when the adhesive used is NIVELANTE 80.



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